juurihormonia

Juurihormoni, also known as auxins, are a class of plant hormones that play a crucial role in plant growth and development. The term "auxin" is derived from the Greek word "auxein," meaning "to grow." These hormones are primarily synthesized in the apical meristems of shoots and roots, as well as in young leaves and developing seeds.

One of the primary functions of juurihormoni is to promote cell elongation. They achieve this by loosening the cell walls, allowing the cells to expand under turgor pressure. This process is fundamental to stem and root growth. Juurihormoni also influence tropisms, which are directional growth responses to external stimuli. Phototropism, the bending of plants towards a light source, is mediated by auxins accumulating on the shaded side of the stem, promoting greater cell elongation there. Similarly, gravitropism, the growth of roots downwards and shoots upwards in response to gravity, is also regulated by auxin distribution.

Beyond growth and tropisms, juurihormoni are involved in a variety of other developmental processes. They play a role in apical dominance, the inhibition of lateral bud growth by the terminal bud, ensuring that the plant grows upwards. They are also essential for vascular tissue differentiation, fruit development, and root initiation. The concentration of juurihormoni is critical; high concentrations can inhibit root growth while promoting shoot growth. This differential response is a key aspect of their complex regulatory role in plants.